The present invention relates generally to the use of Ceramic Matrix Composite liners in a gas turbine engine combustor and, in particular, to the damping of vibrations experienced by the combustor.
It will be appreciated that the use of non-traditional high temperature materials, such as Ceramic Matrix Composites (CMC), are being studied and utilized as structural components in gas turbine engines. There is particular interest, for example, in making combustor components which are exposed to extreme temperatures from such material in order to improve the operational capability and durability of the engine. As explained in U.S. Pat. No. 6,397,603 to Edmondson et al., substitution of materials having higher temperature capabilities than metals has been difficult in light of the widely disparate coefficients of thermal expansion when different materials are used in adjacent components of the combustor. This can result in a shortening of the life cycle of the components due to thermally induced stresses, particularly when there are rapid temperature fluctuations which can also result in thermal shock.
Accordingly, various schemes have been employed to address problems that are associated with mating parts having differing thermal expansion properties. As seen in U.S. Pat. No. 5,291,732 to Halila, U.S. Pat. No. 5,291,733 to Halila, and U.S. Pat. No. 5,285,632 to Halila, an arrangement is disclosed which permits a metal heat shield to be mounted to a liner made of CMC so that radial expansion therebetween is accommodated. This involves positioning a plurality of circumferentially spaced mount pins through openings in the heat shield and liner so that the liner is able to move relative to the heat shield.
U.S. Pat. No. 6,397,603 to Edmondson et al. also discloses a combustor having a liner made of Ceramic Matrix Composite materials, where the liner is mated with an intermediate liner dome support member in order to accommodate differential thermal expansion without undue stress on the liner. The Edmondson et al. patent further includes the ability to regulate part of the cooling air flow through the interface joint.
Another concern with the implementation of CMC liners is reducing the amount of vibration experienced by such combustor. It has been learned that replacing traditional metal liners with CMC liners causes the vibration response of the combustor to drop into the operating range of the engine. This appears to stem from the radially free manner of mounting the liners at a forward end, as described in a patent application entitled xe2x80x9cMounting Assembly For The Forward End Of A Ceramic Matrix Composite Liner In A Gas Turbine Engine Combustor,xe2x80x9d having Ser. No. 10/324,871 and being owned by the assignee of the present invention, as well as the radially free manner of mounting the liners at an aft end, as described in a patent application entitled xe2x80x9cMounting Assembly For The Aft End Of A Ceramic Matrix Composite Liner For A Gas Turbine Engine Combustor,xe2x80x9d having Ser. No. 10/326,209 and being owned by the assignee of the present invention.
Accordingly, it would be desirable for a support member to be developed for use with a combustor having a CMC liner, where such support member is able to stiffen the combustor and increase the frequency out of the operating range of the engine. It is also desirable for the support member to have a geometry which minimizes blockage of air flow.
In accordance with a first exemplary embodiment of the invention, a support assembly for a gas turbine engine combustor including an inner liner and an inner casing spaced therefrom is disclosed, wherein a longitudinal centerline axis extends through the gas turbine engine. The support assembly includes an annular inner support cone located adjacent an aft end of said inner liner, an annular nozzle support connected to the inner support cone, and a plurality of support members connected at a first end to a forward end of the inner liner and connected at a second end to the inner support cone.
In accordance with a second exemplary embodiment of the invention, a combustor for a gas turbine engine having a longitudinal centerline axis extending therethrough is disclosed as including: an inner liner having a forward end and an aft end, where the inner liner is made of a ceramic matrix composite material; an inner casing spaced from the inner liner so as to form an inner passage therebetween; an annular inner support cone located adjacent to the inner liner aft end, where the inner support cone is made of a metal; and, a plurality of circumferentially spaced support members connected at a first end to the inner liner forward end and connected at a second end to the annular inner support cone. In this way, the support members provide additional stiffness to the combustor and cause the vibrations experienced by the combustor to be outside the operating frequency of the gas turbine engine.
In accordance with a third embodiment of the invention, a method of providing additional stiffness to a gas turbine engine combustor is disclosed, wherein an inner liner of the combustor is connected at a forward end and at an aft end in a manner permitting radial movement. The method includes the steps of movably connecting a plurality of support members at a forward portion to a forward end of the inner liner and fixedly connecting the support members at an aft portion to an annular inner support cone. Additional steps of the method may include fixedly connecting the support members at a forward portion to a dome and/or an inner cowl of the combustor.